The present invention relates to frictional surfaces of brake disks, wherein the frictional properties are improved by the employment of reinforcement material substantially throughout the depth of the frictional surfaces.
Heretofore, a multitude of structures for frictional engagement of two materials have been disclosed. More particularly, these frictional surfaces have found great utility in braking mechanisms for various vehicles and machinery, clutch mechanisms for the same, and other devices which require the engagement of two materials along an axis where no interlocking engaging means can exist.
Because the frictional surfaces must withstand the tremendous pressures and temperatures exerted by contact of the two materials, the materials comprising these frictional surfaces have generally been made from carbonized material or various metals. These materials are generally bonded to the internal structural supports, and the entire frictional properties of the system depend on the type of material employed. Examples of this type of frictional structure have been disclosed by U.S. Pat. Nos. 1,935,713; 2,821,271; 2,973,336; 2,251,410; 2,783,529; 2,966,737; 2,850,118 and 3,191,734. The structure taught by each of these patents do not rely on any other material for additional support and resistance to the frictional strain.
Other approaches to the design of a good frictional surface which may be reinforced by various structures to improve its frictional properties and intended purposes. In some cases, the art has taught the employment of reinforcement means for engaging the frictional material to the supporting structure of the entire system. In this manner, greater anchoring of the frictional material to the supporting hardware of the system is achieved. There is no effect on the frictional characteristics of the frictional material along its surface. U.S. Pat. No. 1,470,475, U.S. Pat. No. 1,880,750, U.S. Pat. No. 2,911,074, and U.S. Pat. No. 2,948,361 disclose this structure as described, whereby reinforcement material secures the frictional material to the supporting structure. Frictional material reinforced only near the supporting structure does not adequately prevent spalling of the frictional surface upon contact with other surfaces during use.
Another reinforcement system teaches the placing of the reinforcement material entirely within the frictional material, whereby greater internal structural support of the frictional material is achieved. This internal reinforcement may assume a variety of configurations, including a special structure for later securing that embedded material to the supporting structure of the frictional system. U.S. Pat. Nos. 1,182,368; 2,464,437; 2,818,634; 3,064,343 and 3,698,526 disclose internally embedded reinforcement of the frictional material. Reinforcement material embedded within the frictional material but not connected to other reinforcement material or the upper or lower surface of the frictional material does not provide adequate reinforcement throughout the entire volume of the frictional material.
Yet another type of reinforcement mechanism is the employment of reinforcement materials at the outer surface of the frictional material. As disclosed by U.S. Pat. Nos. 2,160,770 and 2,728,700, exposure of the reinforcement material at the surface of the frictional material is designated for increased wear resistance without support of the reinforcement material back to the supporting structure of the frictional system. Reinforcement material contained in the frictional material at the functional surface does not provide adequate reinforcement of the frictional material near the supporting structure of the frictional system.
In some designs, the reinforcement material has been placed in uniform layers or disparate scattering to assure reinforcement in a direction parallel to the frictional surface of the entire system. U.S. Pat. No. 587,493, U.S. Pat. No. 2,747,701, U.S. Pat. No. 3,345,734, and U.S. Pat. No. 3,390,750 disclose systems where the reinforcement material is interlocked or associated in a direction parallel to the frictional surface. Horizontal reinforcement material throughout the frictional material without vertical interconnection provides a layered reinforcement mechanism which does not adequately reinforce the full depth of the frictional material.
Reinforcement of the frictional surfaces to the frictional system has assumed a direction perpendicular to the frictional surface. As disclosed by U.S. Pat. No. 374,427, this reinforcement may be achieved by the use of soft metal rods embedded in the cast iron frictional material. There is no interconnection provided between the various rods in the frictional system, which seriously limits the scope of interconnected reinforcement. Likewise, the use of thin partition members as vertical members is disclosed by U.S. Pat. No. 1,557,668. In this patent, the thin partition members provide separation of the composition during the manufacture of the frictional system. The vertical partition members are removed after initial formation of the composition comprising the frictional material, their presence being required to separate various formulae of composition for the frictional material during the process of manufacture. Vertical reinforcement material in the frictional material as taught by these two patents does not provide adequate reinforcement across the width of the frictional material.
U.S. Pat. No. 199,161 discloses a system whereby the frictional material is embedded in a frame composed of a material having less desirable frictional characteristics. Through this system of embedment, the frictional material is restrained in position by the formation of the frame. Placing the frictional material in a frame provides outside support but achieves no inner reinforcement.
U.S. Pat. No. 3,534,464 discloses the material of the frame extending into the saucer reserved for the frictional surface. This additional framework within the saucer provides additional reinforcement of the frictional material in the saucer to the frictional system. This reinforcement comprising a ribbed structure is welded in place in the saucers at the same time the frictional surfaces are sintered during assembly of the entire frictional system. The welded junction of the ribbed structures secures the reinforcement, against which the frictional material is sintered. Incorporating an internal welded framework into the area in which the frictional material resides cannot adequately reinforce the frictional material without becoming a frictional component itself and thereby having to exhibit frictional properties compatible with the frictional material itself.
U.S. Pat. No. 3,391,763 discloses a frictional system having rod-shaped heat transfer elements located on the obverse side of the frictional system. This structure provides ventilation to those heat transfer elements with a system of spacers embedded in the obverse side of the frictional system. Use of heat transfer elements to the obverse side of a frictional surface does not reinforce the frictional material at the frictional surface.
Besides resisting breakdown as caused by the results of destructive frictional forces, the frictional system must serve its purpose of providing a good frictional contact at its surface to engage other surfaces and transfer or inhibit power and momentum. The placing of too many reinforcement materials not having the same frictional coefficient as the frictional material disrupts the beneficial performance of the frictional system, even though the durability of the frictional system is enhanced. The reinforcement material supplants the frictional material as the true frictional surface, thereby seriously affecting overall beneficial frictional performance.